Demands on critical dimension specifications increase with the continuous shrinking of design rules. In order to meet sub-0.13μm specifications with precise process control, a better understanding of the etching chemistry and surface reactions need to be achieved. Optical emission spectroscopy (OES) is frequently used in the photomask community as a diagnostic for calling endpoint, but is often underutilized in process development. In-situ measurements, like OES, need to be utilized and correlated to post-etch metrology measurements in order to provide a larger picture of the etch process.
In this paper, OES is used to characterize and monitor chrome etch processes on the Etec Systems Tetra photomask etch chamber. Changes in process conditions, such as source power, He percentage, pressure, and Cl2:O2 flow ratios have been captured by time-averaged optical emission traces. The OES data of the plasma, along with SEM pictures of line profiles, are used to gain insight in process optimization for the etching of chrome.